DEATH FROM THE SKIES!

A surprisingly upbeat look at all the ways the universe can destroy us.

After a brief introduction, astronomer Plait (Bad Astronomy, 2002) gets down to business with asteroid strikes. The chapter begins with a fictionalized episode that leads to the arrival of the killer planetoid. The author then steps back to relate the science: what meteors are, how often they hit Earth, evidence that very large ones have done so (including the famous dinosaur-killer 65 million years ago) and the probability that it will happen again. He points out that unlike many other disasters, this one is potentially preventable if humans make it a priority to find and deflect possible impactors. Plait then moves on to the next killer: a hyperactive sun. Each chapter introduces a new, plausible and usually unstoppable cosmic disaster: nearby supernovae, cosmic ray bursts, black holes, hostile aliens—ending with (in order) the eventual deaths of the sun, the galaxy and the universe as a whole. He also calculates the probability of each occurrence. More interestingly, Plait uses each of the doomsday scenarios to teach about astronomy and physics. The supernovae chapter includes material on the history of science, stellar evolution, astrophysics and day-to-day astronomy. For example, some 100 tons of material from the Crab Nebula supernova, which was seen exploding nearly 1,000 years ago, will eventually impact Earth. That sounds like a lot, but 20 to 40 tons of meteoric material impacts our planet every day, so the effect of the Crab will be at most a blip. The text is full of similar mundane facts, related clearly and logically to the sensational scenarios, the author’s purported subject. An epilogue gives the odds on different types of cosmic doom. Readers will be glad to know that most of them are extremely unlikely—at least in their lifetimes.